WOUNDS 



27 



WOUNDS 



Wounds may conveniently be arranged under two distinct 

 headings: (i) natural wounds, effected by the plant itself for 

 economic reasons ; (2) wounds resulting from outside in- 

 fluence, as pruning, birds, game, insects, storms, grass-cutting 

 machines, etc. 



Self pruning. Many different kinds of trees shed certain 

 of their twigs annually, as the litter of twigs under such trees 



FlG. 2. An example of good pruning. The wound was 

 at once protected by a coating of gas-tar, and is nearly 

 covered by a development of callus. The figure represents 

 portion of a poplar growing in Kew Gardens. Much re- 

 duced. 



clearly indicates. The plant anticipates the fall of certain 

 branches some time in advance, by forming a layer of peri- 

 derm across the branch at the point where the portion no 

 longer required is to be cut off, so that when the twig actually 



